Abstract

Variability of multi-joint essential tremor (ET) between patients and within the two upper limbs makes a visual assessment for the determination of botulinum toxin type A (BoNT-A) injections challenging. Kinematic tremor analysis guidance has succeeded in overcoming this challenge by making effective long-term unilateral BoNT-A injections for disabling ET. In this open-label study, 31 ET participants received three bilateral arm BoNT-A injection cycles over 30 weeks with follow-ups six-weeks post-treatment. Whole-arm kinematic assessment of tremor using a customized, automated algorithm provided muscle selection and dosing per muscle without clinician’s assessment. Efficacy endpoints included Fahn-Tolosa-Marin tremor scale, quality of life (QoL) questionnaire, and maximum grip strength. BoNT-A reduced tremor amplitude by 47.7% in both the arms at week-6 (p < 0.005) that persisted from weeks 18–30. QoL was improved by 26.5% (p < 0.005) over the treatment period. Functional interference due to tremor was reduced by 30% (p < 0.005) from weeks 6–30. Maximum grip strength was reduced at week 6 (p = 0.001) but was not functionally impaired for the participants. Effective bilateral ET therapy by personalized BoNT-A injections could be achieved using computer-assisted tremor analysis. By removing variability inherent within the clinical assessments, this standardized tremor analysis method enabled patients to have improved bimanual upper limb functionality after the first treatment.

Highlights

  • During the first year of diagnosis, 30% of essential tremor (ET) patients are non-responders to oral medication, while in the following year, an additional 30% of patients discontinue their treatment due to a lack of satisfaction from poor functional benefit and an increase in adverse effects [1,2]

  • In our studies, personalized therapy of botulinum toxin type A (BoNT-A) was achieved using computer-assisted, kinematic tremor analysis at the wrist, elbow, and shoulder aiding the clinical judgment of injection parameters [4]

  • BoNT-A injection parameters can be fully determined by this computer-assisted tremor analysis

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Summary

Introduction

During the first year of diagnosis, 30% of essential tremor (ET) patients are non-responders to oral medication (e.g., primidone, propranolol), while in the following year, an additional 30% of patients discontinue their treatment due to a lack of satisfaction from poor functional benefit and an increase in adverse effects [1,2]. Upper limb tremor severity can be further worsened causing disability to bimanual arm function, during activities of daily living, for work-related tasks, and impairs quality of life (QoL). Toxins 2019, 11, 125 in their most disabling tremulous arm, as perceived by the patient, with personalized botulinum toxin type A (BoNT-A) injections [3,4]. The importance of using a personalized BoNT-A approach for treating tremor has been supported by recent clinical studies as the best method to achieve tremor reduction with minimal hand weakness [6,7]. In our studies, personalized therapy of BoNT-A was achieved using computer-assisted, kinematic tremor analysis at the wrist, elbow, and shoulder aiding the clinical judgment of injection parameters (the selection of arm muscles contributing to tremor and the appropriate dose per muscle) [4]. BoNT-A injection parameters can be fully determined by this computer-assisted tremor analysis

Methods
Results
Conclusion

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